1. Technical Field
The present invention relates to a liquid discharging apparatus such as an ink jet type printer and a control method of a liquid discharging apparatus.
2. Related Art
As a liquid discharging apparatus, there is a liquid discharging apparatus constituted so as to create a pressure change to liquid in a pressure generation chamber (a kind of pressure chamber) by generating a driving signal including a driving pulse (a discharge pulse) and applying (supplying) the generated driving pulse to a pressure generation element (for example, a piezoelectric vibrator, a heat generation element, or the like), thereby driving the pressure generation element, and to discharge liquid from a nozzle orifice communicated with the pressure generation chamber by using the pressure change. Also, in the liquid discharging apparatus constituted so as to generate a plurality of driving pulses which drives the pressure generation element, a micro-vibration pulse, which vibrates ink in the nozzle orifice to the extent that does not discharge ink from the nozzle orifice, is often supplied to the pressure generation element when ink is thickened due to exposure of a meniscus (a free surface of ink in the nozzle orifice) from the nozzle orifice, or the like.
The micro-vibration pulse is constituted to include a first charging element which changes voltage from a reference voltage up to a micro-vibration voltage, a first electrical discharge element which changes voltage from the micro-vibration voltage up to an intermediate voltage set between the reference voltage and the micro-vibration voltage, a second charging element which changes voltage from the intermediate voltage up to the micro-vibration voltage, and a second electrical discharge element which changes voltage from the micro-vibration voltage up to the reference voltage, as typified by, for example, JP-A-2007-260933, and by providing a plurality of kinds of vibrations, in which changes in voltage are different from each other, to ink in the pressure generation chamber or the meniscus in the nozzle orifice by supply of each of these elements, in which a voltage changing direction and an amount of change are different from each other, to the pressure generation element, and agitating ink by the vibrations, thickening of ink is suppressed.
However, in a case where natural thickening of ink is promoted, even if pressure fluctuations are provided, since it becomes more difficult for shaking of ink to occur, a need to further increase an agitation effect of ink in the pressure generation chamber arises. For this reason, consideration has been given to supplying a micro-vibration waveform, in which only a voltage change amount is increased, to the pressure generation element. However, up until now, in a case where a voltage change amount of a micro-vibration pulse is increased, with respect to residual vibration of the meniscus due to supply of the charging element to the pressure generation element, pressure fluctuations by an electrical discharge element which subsequently occurs are added, so that vibration of the meniscus is amplified, whereby there is a fear that ink will be erroneously discharged from the nozzle orifice. Also, in order to prevent this erroneous discharge, consideration has been given to increasing a duration which supplies the electrical discharge element of the micro-vibration pulse. However, since a waveform length of the entire micro-vibration pulse is lengthened, there is a problem in that high-frequency driving becomes impossible or the degree of freedom of design of a waveform is decreased.